1. Field of Invention
The invention relates to a method for removing material from a substrate, and in particular, a method for selectively removing silicon nitride from a substrate.
2. Description of Related Art
Typically, during fabrication of integrated circuits (ICs), semiconductor production equipment utilize a (wet) etching or cleaning process to remove or etch material from target locations on a semiconductor substrate. The success of the etching process requires an etching chemistry that includes chemical reactants suitable for selectively removing one material while substantially not removing another material. Various compositions have been developed for removal of specific classes of materials from substrates in semiconductor wafer technologies.
For example, silicon nitride is commonly used in semiconductor processing as a cap layer, spacer layer, or hard mask layer, to name a few, during the formation of various devices. In these processing techniques, at least a portion of the silicon nitride layer is selectively removed via an etching process. In particular, the silicon nitride layer is selectively removed relative to silicon oxide. One technique includes submersing the substrate comprising silicon nitride in a bath of boiling H3PO4, which has been shown to achieve a selectivity of about 35:1 for etching silicon nitride relative to silicon dioxide.
However, even with this success, it remains desirable to identify alternative techniques and compositions for treatment of substrates, particularly to remove nitride materials, especially silicon nitride, from substrates such as semiconductor wafers with selectivity to, for example, silicon and silicon-germanium alloys.